1. Field of the Invention
The invention relates to a deployable lattice column incorporating rigid diagonal members, which members significantly increase the torsional stiffness of the deployed column when compared to the torsional stiffness of such a column with flexible diagonal members.
2. Prior Art
Deployable lattice columns are used in a variety of environments, including both space and terrestrial applications. In many of these environments, the deployed column will be subjected to physical forces challenging its integrity. For example, the column may be used to elevate and support a dish antenna. Weather forces acting on the antenna can and will impart severe strain to the column.
In a deployable lattice column such as described in U.S. Pat. No. 3,486,279 or U.S. Pat. No. 4,334,391, flexible diagonal members are employed to stiffen the column. In some designs, such flexible members each include a latching mechanism that allows a change in diagonal length during packaging. Such flexible members significantly contribute to the ability of such a lattice column to be deployed from a collapsed state; in fact, some people have even considered such columns to require the use of flexible diagonal members. However, when a torsional load is imparted to such a column, for example by wind forces buffeting a supported dish antenna, the resulting twisting of the column can cause various of the diagonal members to slacken, thereby significantly degrading the stiffness of the column and, in response to severe forces, contributing to failure of the column. Also, flexible diagonal members with latching mechanisms complicate and slow both deployment and retraction of the column.
It is an object of this invention to provide a deployable lattice column of significantly increased torsional strength when compared to deployable lattice columns of the prior art. It is also an object of this invention to provide a deployable lattice column with rigid diagonal members of a fixed length. It is another object of this invention to achieve such a column without substantially increasing its overall size or its collapsed volume. These and other objects will appear from the following description of a preferred embodiment.